Color

A 32-color palette has been developed for the GNOME desktop. The palette may be downloaded from http://developer.gnome.org/projects/gup/images/ximian-palette. To use it in The GIMP, save it to your ~/.gimp_1.2/palettes folder, and restart The GIMP. A single, consistently-used palette helps give a unified look and feel to the desktop while minimizing visual distractions. If you need a color that is darker or lighter than the colors in this basic palette (e.g., for anti-aliasing), choose a color that is closest to the hue you need, then darken or lighten as required.

Figure 8-1 The basic GNOME 32-color palette

Table 8-1 RGB and hexadecimal values for the basic palette

Color	Description	RGB	Hex	Color	Description	RGB	Hex
	Basic 3D Hilight	234 232 227	#EAE8E3		Basic 3D Medium	186 181 171	#BAB5AB
	Basic 3D Dark	128 125 116	#807D74		3D Shadow	86 82 72	#565248
	Green Hilight	197 210 200	#C5D2C8		Green Medium	131 166 127	#83A67F
	Green Dark	93 117 85	#5D7555		Green Shadow	68 86 50	#445632
	Red Hilight	224 182 175	#E0B6AF		Red Medium	193 102 90	#C1665A
	Red Dark	136 70 49	#884631		Red Shadow	102 56 34	#663822
	Purple Hilight	173 167 200	#ADA7C8		Purple Medium	136 127 163	#887FA3
	Purple Dark	98 91 129	#625B81		Purple Shadow	73 64 102	#494066
	Blue Hilight	157 184 210	#9DB8D2		Blue Medium	117 144 174	#7590AE
	Blue Dark	75 105 131	#4B6983		Blue Shadow	49 78 108	#314E6C
	Face Skin Hilight	239 224 205	#EFE0CD		Face Skin Medium	224 195 158	#E0C39E
	Face Skin Dark	179 145 105	#B39169		Face Skin Shadow	130 102 71	#826647
	Accent Red	223 66 30	#DF421E		Accent Red Dark	153 0 0	#990000
	Accent Yellow	238 214 128	#EED680		Accent Yellow Dark	209 148 12	#D1940C
	Accent Green	70 160 70	#46A046		Accent Green Dark	38 199 38	#267726
	White	255 255 255	#ffffff		Black	0 0 0	#000000

Users with vision disorders, such as color-blindness or low vision, require alternatives to default settings. A good user interface anticipates these needs by providing customizable preferences and support for accessible themes. Even better is an application that is already configured with carefully-chosen color and contrast defaults.

An estimated 11% of the world population has some sort of color-blindness. Those affected typically have trouble distinguishing between certain hues such as red and green (deuteranopia or protanopia), or blue and yellow (tritanopia). Therefore it is necessary to allow the user to customize colors in any part of your application that conveys important information. This means that your application must effectively convey information using just the colors from any theme that the user chooses.

A useful tool for reviewing information about color-blindness and checking legibility of images for color-blind users is Vischeck, an online tool that simulates the way an image or a website might appear to a user who has deuteranopia, protanopia, or tritanopia.

Figure 8-2 How the earth looks to a user with normal color vision (left), deuteranopia (middle), and tritanopia (right). (Images from http://www.vischeck.com).

Other users have more problems with contrast levels rather than hue on their screen. Some users require a high level of contrast between background and foreground colors, such as black on white, white on black, or some other high-contrast combination. Others can experience discomfort unless they use low-contrast settings, such as gray text on a lighter gray background.

You can meet these needs by ensuring your application supports the accessible GNOME themes (found in the gnome-themes module in cvs), which include high and low contrast themes, and large print themes. This means you must supply default and large sizes of high-, low- and regular-contrast icon sets with your application.